Incorporating Dual-Polarization Signatures into the Tornado Warning Process for Supercells: ZDR/KDP Separation and Size Sorting Signals

Previous field studies investigated the possibility of utilizing the dual-polarization radar fields of differential reflectivity (Z_DR) and specific differential phase (K_DP) to help discriminate between tornadic and non-tornadic storms. The main strategy evaluated the character of preferential drop size sorting to infer trends in storm-scale shear. Later research demonstrated through use of idealized numerical simulations that hydrometeor size sorting is not fundamental to wind shear, but rather to the storm-relative flow itself. It was also noted that, when using the degree of drop size sorting as a proxy (particularly) in supercell environments, storm-relative flow and lower tropospheric storm-relative helicity are likely well correlated. As such, it is hypothesized that in supercell environments patterns of Z_DR and K_DP can identify important trends in storm-relative flow and storm-relative helicity, thereby helping to diagnose a storm’s tornadic potential.

In an attempt to leverage study results and test hypotheses outlined above, a number of tornadic and non-tornadic supercell cases were evaluated. While previous field studies were conducted in specific geographical regions of the United States, this study has looked at a broad array of cases east of the Rocky Mountains, in an effort to find a unified, geographically independent approach to using dual-polarization radar fields for better discrimination between tornadic and non-tornadic storms. Applicable findings center on separation characteristics between Z_DR areal maxima in the Z_DR arc region and K_DP areal maxima within the K_DP foot.

Initial attempts, as well as future projections, to incorporate study results into National Weather Service warning operations will also be discussed.